Concrete pavement cutting machine

ABSTRACT

A mobile frame has a mounting platform underlying the mobile frame which is mounted for swinging movements toward and away from the upper surface of a strip of concrete pavement at a constant degree of angular relationship with the pavement. A plurality of cutting discs are mounted in tandem on the platform for rotation in a common vertical frame. Hydraulic power devices driven by an engine and control apparatus are provided to drive the cutting discs, impart movements to the platform, and impart steering and driving movements to the wheels of the mobile frame. A flow of liquid coolant is provided for the cutting discs and the cutting discs are so disposed relative to the mobile frame that each disc rearwardly of the front disc cuts into the pavement at a greater depth from the surface of the pavement than the preceding disc. A trolley device connected to the steerable wheels of the mobile frame guides the mobile frame in its path of travel along the pavement.

United States Patent [1 1 Binger et al.

[ Aug. 26, 1975 CONCRETE PAVEMENT CUTTING MACHINE [75] Inventors: Wynn S. Binger, Eden Prairie;

Robert E. Shope, Apple Valley, both of Minn.

[73] Assignee: Construction Materials, Inc.,

Minneapolis, Minn.

[22] Filed: Oct. 30, 1974 [21] Appl.No.: 519,344

3,796,462 3/1974 Staub 299/39 Primary ExaminerErnest R. Purser Attorney, Agent, or Firm-Merchant, Gould, Smith &

Edell 5 7 ABSTRACT A mobile frame has a mounting platform underlying the mobile frame which is mounted for swinging movements toward and away from the upper surface of a strip of concrete pavement at a constant degree of angular relationship with the pavement. A plurality of cutting discs are mounted in tandem on the platform for rotation in a common vertical frame. Hydraulic power devices driven by an engine and control apparatus are provided to drive the cutting discs, impart movements to the platform, and impart steering and driving movements to the wheels of the mobile frame. A flow of liquid coolant is provided for the cutting discs and the cutting discs are so disposed relative to the mobile frame that each disc rearwardly of the front disc cuts into the pavement at a greater depth from the surface of the pavement than the preceding disc. A trolley device connected to the steerable wheels of the mobile frame guides the mobile frame in its path of travel along the pavement.

15 Claims, 10 Drawing Figures PATENTED M182 6 [97s snzn u 0; 4.

FIG. i0

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CONCRETE PAVEMENT CUTTING MACHINE BACKGROUND OF THE INVENTION This invention is in the nature of a modification of pavement cutting apparatus as disclosed and claimed in US. Pat. Nos. 3,547,492 issued to Wynn S. Binger and 3,785,705 issued to Wynn S. Binger, et al and is devised for the purpose of controlling the cracking of concrete pavement. This machine is intended to cut a single slot in concrete aprons, down the center of a roadway pavement or a stretch of airplane runway to control cracking of the apron, pavement or runway caused by expansion/contraction in areas having wide seasonal temperature variations. The cracking or fracture of the concrete normally occurs at random spacing and along crooked lines leading to an unsightly appearance and often resulting in weakened portions as well as portions which may be disposed at slightly different elevations. ln slotting the aprons, pavement or runway, a 2% inch deep slot is generally sufficient for a concrete thickness from 4 to 6 inches thick and a 3 inch deep slot appears to be satisfactory for slotting concrete between 6 and I2 inches thick. A particular problem in cutting slots of this magnitude is that a single expensive cutting disc is subjected to extreme wear and abuse and the cutting machine must frequently be shut down to replace such worn cutting discs. If the travel of the cutting machine is slowed in an attempt to overcome the abuse to the cutting discs, the time element needed to accomplish the cutting job is prohibitively expensive. Also, it is practically impossible to make repeated cuts of lesser depth with a single cutting disc without varying from the path of travel of the preceeding cut or cuts.

SUMMARY OF THE INVENTION With the above in mind, a concrete pavement cutting machine is provided which includes a mobile frame having fixed and steerable wheels mounted for movement of the frame along a path of travel. A mounting platform underlies the mobile frame and a plurality of arms mounts the platform for swinging movements toward and away from the concrete pavement underlying the mobile frame at a constant degree of angular relationship with the plane of the concrete pavement. A plurality of cutting discs are mounted in tandem on the platform for rotation in a common vertical plane extending longitudinally of the direction of travel of the mobile frame. Hydraulic devices driven by an engine impart driving movements to the cutting discs, impart movement to the platform, impart driving movements to the wheels, and impart steering movements to steerable wheels of the mobile frame. A flow of liquid coolant is introduced to each of the cutting discs and the cutting discs are so disposed relative to the mobile frame that each disc rearwardly of the front one of the discs cuts into the pavement at a greater depth from the surface of the pavement than the preceeding disc.

An important object of this invention is the provision of a pavement cutting machine which can relatively quickly and easily cut a groove extending longitudinally along a concrete pavement or runway so as to promote cracking or fracture of the pavement or runway within the groove.

Another object of this invention is the provision of a machine of the class above described which will cut a groove longitudinally in a strip of concrete pavement within a minimum amount of time and with a minimum amount of abuse or wear to the cutting discs of the machine.

A still further object of the present invention is the provision of a machine of the class above described which is operable to cut grooves in concrete aprons as well as strips of concrete pavement.

These and other important objects will become apparent to those skilled in the art upon consideration of the following detailed specification, appended claims and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in top plane of a concrete pavement cutting machine constructed in accordance with the present invention and showing its operative position in relation to a strip of concrete pavement;

FIG. 2 is an enlarged side elevational view of the invention as seen generally from the line 2-2 of FIG. 1, portions thereof being broken away and shown in section;

FIG. 3 is a view in horizontal section as seen generally from the line 3-3 of FIG. 2;

FIG. 4 is a view in transverse vertical section as seen generally from the line 4-4 of FIG. 2, portions thereof being broken away;

FIG. 5 is a view in vertical section as seen generally from the line 5-5 of FIG. 4, portions thereof being broken away;

FIG. 6 is an enlarged vertical section as seen from the line 6-6 of FIG. 5;

FIG. 7 is a view in horizontal section as seen generally from the line 7-7 of FIG. .6;

FIG. 8 is a detail view illustrating a portion of the guide mechanism for the present invention, as seen generally from the line 8-8 of FIG. 1;

FIG. 9 is a schematic diagram of the hydraulic system utilized to drive the cutting discs of the present invention; and

FIG. 10 is a schematic diagram of the hydraulic mechanism utilized to impart raising and lowering movements to the cutting discs and to impart steering and driving movements to the mobile frame of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring in detail to the drawings wherein like reference characters indicate like parts throughout the several views, the reference numeral 10 generally indicates a concrete pavement cutting machine constructed in accordance with the present invention. Cutting machine 10 comprises a mobile frame 11 including fixed and steerable wheel mechanisms 12 and 13. Wheels 12, 13 are mounted for movement of the frame along a path of travel such as that which is defined by the strip of concrete pavement 14 illustrated in FIG. I of the drawings. A mounting platform 15, disposed to underlie the mobile frame 11, is mounted for swinging movements toward and away from an upper surface of the concrete pavement 14 at a constant degree of angular relationship with the plane of the concrete pave ment 14. Means for mounting the platform 15 for the above movements include a pair of front arms 16 and a pair of rear arms 17. Each of the pairs of arms 16, 17 are pivotally connected to respective front and rear portions of the platform 15 and to the frame 11 in a parallelogram arrangement to effect the proper relationship of the platform relative to the upper surface of the pavement 14.

A plurality of cutting discs 2la-21c are mounted in tandem on the platform 15 for rotation in a common vertical plane extending longitudinally of the direction of travel of the mobile frame 1 1. As shown, each of the cutting discs 21a-2lc is fixedly secured to one end of an axle 22 rotatably mounted on the platform 15 by suitable bearing members. Hydraulic power means for driving the cutting discs 21a-21c include an engine 23 and a transmission mechanism 24 coupled to the power output shaft, not shown, of the engine 23. The hydraulic power means further include a plurality of hydraulic motors 25a-25c. The power output shaft, not shown, of each of the motors 25a-25c is coupled to each of the axles 22 of respective cutting discs 21a-2lc whereby rotation of the output shafts of the motors 25a-25c directly drive the shafts 22 of respective cutting discs 21a-21c. A plurality of hydraulic pumps 26a-26c are mounted on the transmission 24 to be driven by the engine 23 in a manner not specifically shown, but well known to those skilled in the art. Each of the hydraulic pumps 26a-26c is operatively connected to a source of fluid contained within a reservoir 27 by means of flexible conduits indicated generally by the numeral 28 and to respective hydraulic motors 25a-25c by flexible fluid conduits 29 as more fully described hereinafter. Each of the fluid conduits 28 has a fluid filter 30 interposed therein to filter fluids from reservoir 27. As seen particularly in FIGS. 3-5, the platform 15 forms a base for mounting a plurality of rigid conduits extending from the hydraulic motors 25a, 25b. In this manner, connec' tions of the flexible conduits 29 to the hydraulic motors 25a-25c are such that they are positioned in generally underlying relationship to the connections of the flexible conduits 29 to respective hydraulic pumps 26a26c. As such, movement of the platform 15 toward and away from the concrete pavement 14 results in the flexible conduits bending in generally flat planes whereby a minimum of rotational forces are exerted on the connections of the flexible conduits 29 to respective hydraulic pumps and motors during such movement of the platform 15.

Referring now to FIG. 9 of the drawings, a schematic diagram illustrating the preferred method of connect ing the several hydraulic motors 25a-25c to respective hydraulic pumps 26a-26c and to the source of fluid in the reservoir 27 is illustrated. It will be here noted, that each of the hydraulic pumps 26a26c is of a variable delivery reversible type whereby to reverse the direction of rotation of the hydraulic motors 25a-25c as will be presently described. As seen particularly in FIG. 9, the fluid connections between each of the motors 25a-25c and respective pumps 26a-26c include a pair of flexible conduits 29a, 29b which provide for flow of fluid in either direction through the motors 25a-25c. In the preferred embodiment as seen in FIG. 2 of the drawings, the front cutting disc 21a is driven in a clockwise direction while the succeeding discs 21b and 21c are driven in a counterclockwise direction. Thus, for example, the flow of fluid from pump 26a to motor 25a is through flexible conduit 29a and the flow of fluid from pumps 26b and 260 to respective motors 25b, 25(- is through flexible conduits 2917. It has been found that this arrangement for driving the cutting disc 2la2lc' permits the cutting operation to proceed at a faster pace with less strain on the cutting disc. Fluid flowing from the reservoir 27 through the pump 26a-26c and motors 25a-25c is returned to the reservoir 27 through a return conduit 31 connected to each of the pumps 26a-26c and to a manifold 32. Manifold 32, in turn, is connected to the reservoir 27 by means of a return conduit 33.

Because the several motors and pumps must run for extended periods of time and under heavy load conditions, it is desirable to provide some method of cooling the fluids which pass through the pumps and motors from the reservoir 27. In this respect, manifold 32 is provided with a heat exchange coil 34 which is supplied with a liquid coolant (from a source to be presently described) to dissipate the heat from the fluid passing through the manifold 32. Pressure relief is provided for the system through conduits 35 which connect pressure release mechanisms, not shown, within the motors 250-250 to a manifold 36 and thence to the reservoir 27 through a conduit 37.

Referring particularly to FIGS. 2, 4 and 5, the direction of fluid flow and displacement of the pumps 26a through 26c is controlled by means of a level 38 connected to a suitable valve mechanism, not shown, but contained within the housing of each pump 26a-26c. Such valve mechanism is well known in the art and therefor is not shown in detail.

Hydraulic power means for imparting movements to the platform include a hydraulic elevator ram 41 pivotally connected to and extending between the mobile frame 11 and platform 15. A separate hydraulic pump 42 is operatively coupled, by means not shown, to be driven by the engine 23. As shown particularly in FIG. 10 a fluid conduit 43 extends from the source of fluid in the reservoir 27 through the separate pump 42 to a control valve 44. A fluid filter 39 is interposed in the line 43 between the pump 42 and reservoir 27 and thence back to reservoir 27. A pair of fluid conduits 45, 46 extend from the control valve 44 to the, hydraulic elevator ram 41. Operation of the control valve 44 selects the proper conduit 45, 46 to impart raising or lowering movements to the hydraulic elevator ram 41 and platform 15. A manually operated pump 47, interposed in a fluid conduit 48 connected between the fluid conduit 45 and source of fluid in the reservoir 27, is provided to manually operate the hydraulic ram 41 and raise or lower the platform 15 should the separate hydraulic pump 42 fail to operate.

As seen particularly in FIGS. 24 the steerable wheels 13 utilized to guide the mobile frame 11 along a path of travel include a generally inverted U-shaped wheel carriage 51. Wheel carriage 51 is mounted on the mobile frame for rotation on a vertical axis by means of a bolt 52 extending through an upper plate of the carriage 51 and a plate 53 affixed to the underside of the mobile frame 1 l. A sheet of teflon bearing material 54 is interposed between the plate 53 and adjacent surface of the carriage 51 to facilitate rotation of the carriage 51 on the vertical axis of the bolt 52. A tongue 55 is secured to the carriage 51 to extend from the carriage 51 in the direction of travel of the mobile frame 1 1 Hydraulic power means for steering the steerable wheels 13 comprise a hydraulic steering ram 56 which is pivotally connected to and extends between the mobile frame 11 and tongue 55 in a position to cause rotation of the carriage 51 on the vertical axis 52 upon the appropriate introduction of fluid under pressure to the steering ram 56. As seen particularly in FIG. the steering ram 56 is connected to a control valve 57 by means of a pair of fluid conduits 58, 59, the control valve 57 being interposed in the fluid supply line 43 of the separate pump 42. Thus, the control valve 57 controls the direction the wheel carriage rotates on the vertical axis of the bolt 52 by supplying fluid pressure to the appropriate line 58, 59.

In the preferred embodiment, the steerable wheels 13 include at least a pair of wheel members mounted for rotation on a horizontal axle 62 having a rotary axis extending transversely to the direction of travel of the mobile frame 11. The axle 62 is mounted for rotation in suitable bearings carried by the lower ends of the depending legs of the inverted U-shaped carriage 51. The spaced wheel members are fixedly mounted on the axle 62 inwardly of the legs of the U-shaped member 51. Because of the substantial weight of the cutting machine 10 and to add an increased amount of stability to the cutting machine 10, a second pair of wheels are affixed to the axle 62 outwardly of the depending legs of the U-shaped carriage 51.

Hydraulic power means for driving the steerable wheels include a pair of hydraulic wheel motors 63 mounted on the wheel carriage by means of suitable brackets 64. As seen particularly in FIG. 3 of the drawings, a pinion gear 65 is affixed to the output shaft of each of the wheel motors 63. The pinion gears 65 each have meshing engagement with a driven gear 66 carried by a respective steerable wheel affixed to the axle 62 inwardly of the depending legs of the U-shaped carriage 51. As seen particularly in FIG. 3 the axle 62 is formed from separate axle portions joined for independent rotation on aligned axes by means of a coupling 67. In this manner, a differential arrangement is set up betweenthe wheels driven by respective wheel motors 63 to compensate for different speeds of rotation of the wheel members 13 during turning movements imparted by the hydraulic ram 56 to the wheel carriage 51. A control valve 68, interposed in the fluid line 43 from the separate pump 42, is connected to the wheel motors 63 by means of a pair of fluid conduits '69, the wheel motors 63 being connected in parallel in the fluid lines 69. Thus, fluid flowing from the separate pump 42 through the line 43 can be directed into an appropriate one of the fluid conduits 69 by the control valve 68 to cause a rotation of the wheel motors 63 in a direction to drive the steerable wheels 13 in either a forward or a reverse direction.

The speed at which the cutting machine 10 is capable of cutting a concrete pavement is dictated by many variables. For example, recently cured cement can be grooved at a much faster pace than can cement which has been cured for some time. In addition, various mixtures of materials forming the cement dictate the speed at which such cement can be cut by the cutting machine 10. With this in mind, the speed that the machine travels is controlled by a speed control valve 72 interposed in the fluid supply conduit 43 between the control valve 68 and fluid pump 42. A pressure relief conduit 73 extends from a pressure relief valve, not shown, in the speed control valve to the reservoir 27 or the fluid supply conduit 43 at a point downstream of the fluid control valve 68. This provides a flow path for the fluid in line 43 restricted from flowing through the control valve 68 to the motors 63 by the speed control valve 72.

A second reservoir 74 is mounted on the mobile frame 11 in underlying relationship to the fluid reservoir 27. The second reservoir 74 provides a supply of fuel for the engine 23 and serves to position the fluid reservoir 27 whereby the fluid therein is elevated above the level of the several pumps 26a-26c and 42 for selfpriming purposes. The tanks 27, 74 together with the fluids contained therein are positioned on the mobile frame 11 in overlying relationship to the fixed wheels 12 to counterbalance the weight of the engine 23.

Turning now to FIGS. 2-7, the platform 15 includes a shroud 75 which encloses the upper portion of the cutting discs 21a-2lc so as to guard against flying particles during the cutting action of the discs 21a-21c. Means for introducing a flow of liquid coolant to the cutting discs 21a-2lc includes rigid conduits 76 carried by the shroud 75 to extend along opposite side surfaces of each of the cutting discs 2la-2lc. Each of the conduits 76 is formed with apertures 77 adjacent each of the cutting discs 21a-21c to supply the required coolant to such discs. The rigid conduits 76 are connected to a manifold 78 by means of a pair of flexible hose connections 79. A fluid conduit 82, including a shut-off valve 83, leads from the manifold 78 to a source of liquid coolant, not shown, but remote from the cutting machine 10 and which may take the form of a tank truck or the like. As seen in FIGS. 2 and 4, the conduit 82 has the heat exchange coil 34 interposed in series therein so that the liquid coolant flowing through the conduit 82 can be utilized to dissipate the heat within the fluid flowing through the manifold 32 to the reservoir 27 from the pumps 26a-26c. Manifold 78 is provided with control valves to regulate the flow of liquid coolant to opposite sides of the discs 2la-2lc.

The particular means in the preferred embodiment for disposing the cutting discs so they cut into the pavement at a greater depth from the surface of the pavement than the preceding disc include a shim 85. Shim 85 is interposed between the pivotal connection of the rear arms 17 and the frame 1 1. This causes the rear end of the platform 15 to be more closely spaced to the pavement 14 than the front end of the platform 15. In this manner, eachof the cutting discs 21a-21c cut into the concrete pavement a substantially equal amount at progressively greater depths from the surface of the concrete pavement. This, of course, assures that each disc cuts only a portion of the total depth of the groove permitting the cutting machine 10 to progress at a faster rate of travel with less frictional heat build-up and consequently less wear on the particular discs 2la-21c. This arrangement further permits the cutting machine 10 to be operated for extended periods of time without the need to shut down the machine 10 and change the cutting discs 21a-21c as would be the case with the use of but a single cutting disc for cutting the entire depth of the groove. While the preferred method of disposing the cutting discs 21a-21c in the abovedescribed relationship is by interposing a shim 85 as described, it will be appreciated that the platform may be mounted in other ways to position it in the desired relationship with respect to the upper surface of the pavement 14. For example, the shim 85 could as easily be placed between the pivotal connection of the arm 17 to the platform 15 or different thickness shims could be placed between the bearing connecting the axles 22 of the cutting discs 21a-21c to the platform 15. In the preferred embodiment of the invention adjustable stop means in the nature of a flexible cable 86 is provided. Cable 86 extends between the frame 11 and the platform 15 and is'secured in place by means of a suitable releasable clamp 87 and a clevis connection 88. The flexible cable 86 limits downward movement of the platform 15 and parts carried thereby at the desired operational level and supports the platform at such opera tional level with a minimum of strain on the elevator ram 41.

The cutting machine 10 can be steered along a path of travel by the use of steering cylinder 56 in cases where grooves are to be cut in aprons or the like or the cutting machine is to be driven onto a truck or the like for transporting same to other locations. However, it is highly desirable to provide a more efficient method for guiding the machine 10 down a strip of pavement or runway so that the groove indicated by the reference character A in FIG 1 is disposed at a desired dimension between the opposite side edges 14a, 14b of the strip of pavement for runway 14 without'the need for constant correction by an operator of the cutting machine 10. For this purpose, a pair of opposed trolley carriages 89 are provided. Each trolley carriage 89 is constructed to include rollers 90 which have rolling engagement with the upper surface of the pavement 14 and rollers 91 which have rolling engagement with an adjacent one of the opposed side edges 14a, 14b.

A pair of first control rods 92 have opposite ends of each one pivotally connected to a different one of the trolley carriages 89 and to a removable forward extension 55a of the carriage tongue 55. A second pair of control rods 93 have opposite ends of each thereof pivotally connected to a different one of the trolley carriages 89 and to the wheel carriage 51, as at 94. The second pair of control rods 93 function to preclude their respective trolley carriages 89 from trailing rearwardly in response to forward movement of the cutting machine 10. The first control rods 92 are extensible and retractable and are provided with tension means indicated generally by the numeral 95 for biasing each of the first pair of control rods 92 in a direction to re tract the control rods 92 whereby rollers 91 of a respective trolley carriage 89 are maintained in rolling engagement with a respective side edge 14a, 14b of the concrete pavement 14. Each of the second control rods 93 is likewise extensible and retractable to position its respective trolley 89 in an opposed relationship at a desired position relative to the cutting machine 10. A suitable locking device 95 locks the second control rods 93 in a desired position of extensible, retractable adjustment.

Returning to FIGS. 1 and 8 of the drawings, it can be seen that the first pair of control rods 92 each include a pair of telescoping members 92a, 92b, a collar 96 mounted on each of the telescoping members 92a, 92b for adjustment longitudinally thereof and a tension spring 97. Opposite ends of the tension spring 97 are connected to different ones of the collars 96 under a sufficient degree of tension to exert a force to bias the first control rod sections 92a, 92b toward a retracted position. With this arrangement, if the pavement 14 should curve, for example, in a direction towards the side 14b of the trolley carriage 89 engaging the side edge 14b exerts a force through its respective control rod 92 to move the tongue extension 55a in the same direction causing the cutting machine 10 to proceed along its path of travel at the desired distance between the side edges 14a, 14b in spite of a curved portion in the pavement l4. Dimensional differences between the side edges 14a, 14b along the pavement 14 as well as between cooperating first and second control rods 92, 93 and tongue extension 55a are compensated for by the tensioning means 95. In addition, the extensible, retractable feature of the control rods 92, 93 permit the trolley carriages 89 to be adjusted to different widths of pavement 14. It will be appreciated, that the control rods 92 may be adjusted longitudinally by releasing the collars 96 readjusting the members 92a, 92b and reattaching the collars to their respective control rod portions 92, 98 with the spring 97 under the desired degree of tension.

What is claimed is:

1. A concrete pavement cutting machine comprising:

a. A mobile frame including fixed and steerable wheels mounted for movement of said mobile frame along a path of travel;

b. a mounting platform underlying said mobile frame;

0. arm means mounting said platform to said mobile frame for swinging movements toward and away from the concrete pavement underlying said mobile frame at a constant degree of angular relationship with the plane of the concrete pavement;

d. a plurality of cutting discs mounted in tandem on said platform for rotation in a common vertical plane extending longitudinally of the direction of travel of said mobile frame;

e. hydraulic power means including engine means for driving said cutting discs, for imparting said movement to said platform, for driving one of said fixed and steerable wheels and for steering said steerable wheels;

f. Means for adjusting the depth to which said cutting discs cut into the concrete pavement whereby said cutting discs cut into the concrete pavement a substantially equal amount at progressively greater depths from the surface of the concrete pavement; and

g. means for introducing a flow of liquid coolant to each of said cutting discs.

2. The structure of claim 1 in further combination with adjustable stop means for limiting the movement of said platform toward the concrete pavement.

3. The structure of claim 1 wherein each of said cutting discs is fixedly mounted on an axle which is rotatably mounted on said platform, wherein said engine means includes a power transmission and wherein said hydraulic power means for driving said cutting discs includes a hydraulic motor mounted on said platform and coupled to each of said axles, a plurality of hydraulic pumps coupled to said engine transmission, each one of said hydraulic pumps being connected to a different one of said hydraulic motors and to a source of fluid.

4. The structure of claim 3 wherein the connections of said hydraulic pumps to said hydraulic motors includes a plurality of flexible hoses, said flexible hoses being positioned to bend in generally flat planes responsive to movement of said platform whereby a minimum of rotational forces are exerted on the connections of said flexible hoses to respective hydraulic motors and pumps during such movement.

5. The structure of claim 3 wherein the fluid displacement of each of said hydraulic pumps is variable and reversible and each of said pumps includes a fluid return conduit leading to said source of fluid.

6. The structure of claim including a fluid manifold, wherein each of said fluid return conduits is connected to said fluid manifold, and wherein the liquid coolant introducing means includes a fluid conduit having a heat exchange coil passing through said manifold whereby the liquid coolant cools the fluids flowing through said manifold.

7. The structure of claim 3, wherein the hydraulic power means for imparting movement to said platform comprises:

a. a hydraulic elevator ram extending between said mobile frame and platform;

b. a separate hydraulic pump coupled to said engine means;

c. fluid conduits connecting said separate hydraulic pump to said source of fluid and to said hydraulic elevator ram; and

d. control valve means interposed in said fluid conduit for controlling the flow of liquid to said hydraulic elevator ram to impart movement to said pitform toward and away from the concrete pavement.

8. The structure of claim 7 in further combination with manually operated pump means connected to said hydraulic elevator ram and said source of fluid for manually imparting movements to said platform toward and away from the concrete pavement.

9. The structure of claim 7 wherein said steerable wheels include a wheel carriage mounted on said mobile frame for rotation on a vertical axis, a tongue extending from said carriage in the direction of travel of said mobile frame, and wherein said hydraulic power means for steering said steerable wheels comprises:

a. a hydraulic steering ram extending between said frame and carriage so as to cause rotation of said carriage on said vertical axis;

b. fluid conduits connecting said steering ram to said separate pump and source of fluid; and

c. control valve means interposed in said fluid conduits of said steering ram for controlling the move ment of said wheel carriage in opposite directions on said vertical axis.

10. The structure of claim 9 in further combination with a pair of opposed trolley carriages, each trolley of said pair of trolley carriages being constructed to have rolling engagement with the upper surface and a different one of opposed side edges of the concrete pavement, a pair of first control rods having opposite ends of each one pivotally connected to a different one of said trolley carriages and said wheel carriage tongue, a pair of second control rods having opposite ends of each one pivotally connected to a different one of said trolley carriages and said wheel carriage, each of said first and second pair of control rods being extensible and retractable, tension means for biasing each of said first pair of control rods in a direction to retract said control rods whereby each one of said trolley carriages is maintained in rolling engagement with a respective side edge of the concrete pavement and means on each of said second control rods for locking said second control rods against said extensible retractable movements.

ii. The structure of claim 9 wherein said steerable wheels include a pair of spaced wheel members mounted for rotation on a horizontal axis extending transversely to the direction of travel of said mobile frame, a pair of hydraulic wheel motors each operatively coupled to a different one of said wheel members, fluid conduits connecting each hydraulic wheel motor to said separate hydraulic pump, and control valve means for controlling the flow of fluids to said hydraulic motors whereby said hydraulic wheel motors may be stopped and started and operated in forward and reverse directions of rotation.

12. The structure of claim 11 in further combination with a speed control valve connected to said source of fluid and to said control valve means of said hydraulic wheel motors for controlling the speed of operation thereof.

13. The structure of claim 1 wherein said arm means is a pair of front arms and a pair of rear arms each pivotally connected to respective front and rear portions of said platform and said mobile frame in a parallelogram arrangement and wherein said means for adjusting the depth to which said cutting discs cut into the concrete pavement is a shim interposed between said rear pair of arms and said mobile frame.

14. The structure of claim 1 wherein said platform includes a shroud enclosing the upper portion of said cutting discs and wherein said means for introducing a flow of liquid coolant to said cutting discs includes a rigid conduit extending along opposite sides of said cutting discs within said shroud, said conduits being formed with apertures for spraying liquid coolant on opposite sides of each of said cutting discs.

15. A concrete pavement cutting machine comprising:

a. a mobile frame including fixed and steerable wheels mounted for movement of said mobile frame along a path of travel;

b. a mounting platform underlying said mobile frame;

c. arm means mounting said platform to said mobile frame for swinging movements toward and away from the concrete pavement underlying said mobile frame at a constant degree of angular relationship with the plane of the concrete pavement;

d. a plurality of cutting discs mounted in tandem on said platform for rotation in a common vertical plane extending longitudinally of the direction of travel of said mobile frame;

e. hydraulic power means including engine means for driving said cutting discs, for imparting said movement. to said platform, for driving one of said fixed and steerable wheels, and for steering said steerable wheels; and

f. means for introducing a flow of liquid coolant to each of said cutting discs;

g. said cutting discs being so disposed relative to said mobile frame that each disc rearwardly of the front one of said discs cuts into the pavement at a greater depth from the surface of the pavement than the preceeding disc. 

1. A concrete pavement cutting machine comprising: a. A mobile frame including fixed and steerable wheels mounted for movement of said mobile frame along a path of travel; b. a mounting platform underlying said mobile frame; c. arm means mounting said platform to said mobile frame for swinging movements toward and away from the concrete pavement underlying said mobile frame at a constant degree of angular relationship with the plane of the concrete pavement; d. a plurality of cutting discs mounted in tandem on said platform for rotation in a common vertical plane extending longitudinally of the direction of travel of said mobile frame; e. hydraulic power means including engine means for driving said cutting discs, for imparting said movement to said platform, for Driving one of said fixed and steerable wheels and for steering said steerable wheels; f. Means for adjusting the depth to which said cutting discs cut into the concrete pavement whereby said cutting discs cut into the concrete pavement a substantially equal amount at progressively greater depths from the surface of the concrete pavement; and g. means for introducing a flow of liquid coolant to each of said cutting discs.
 2. The structure of claim 1 in further combination with adjustable stop means for limiting the movement of said platform toward the concrete pavement.
 3. The structure of claim 1 wherein each of said cutting discs is fixedly mounted on an axle which is rotatably mounted on said platform, wherein said engine means includes a power transmission and wherein said hydraulic power means for driving said cutting discs includes a hydraulic motor mounted on said platform and coupled to each of said axles, a plurality of hydraulic pumps coupled to said engine transmission, each one of said hydraulic pumps being connected to a different one of said hydraulic motors and to a source of fluid.
 4. The structure of claim 3 wherein the connections of said hydraulic pumps to said hydraulic motors includes a plurality of flexible hoses, said flexible hoses being positioned to bend in generally flat planes responsive to movement of said platform whereby a minimum of rotational forces are exerted on the connections of said flexible hoses to respective hydraulic motors and pumps during such movement.
 5. The structure of claim 3 wherein the fluid displacement of each of said hydraulic pumps is variable and reversible and each of said pumps includes a fluid return conduit leading to said source of fluid.
 6. The structure of claim 5 including a fluid manifold, wherein each of said fluid return conduits is connected to said fluid manifold, and wherein the liquid coolant introducing means includes a fluid conduit having a heat exchange coil passing through said manifold whereby the liquid coolant cools the fluids flowing through said manifold.
 7. The structure of claim 3, wherein the hydraulic power means for imparting movement to said platform comprises: a. a hydraulic elevator ram extending between said mobile frame and platform; b. a separate hydraulic pump coupled to said engine means; c. fluid conduits connecting said separate hydraulic pump to said source of fluid and to said hydraulic elevator ram; and d. control valve means interposed in said fluid conduit for controlling the flow of liquid to said hydraulic elevator ram to impart movement to said platform toward and away from the concrete pavement.
 8. The structure of claim 7 in further combination with manually operated pump means connected to said hydraulic elevator ram and said source of fluid for manually imparting movements to said platform toward and away from the concrete pavement.
 9. The structure of claim 7 wherein said steerable wheels include a wheel carriage mounted on said mobile frame for rotation on a vertical axis, a tongue extending from said carriage in the direction of travel of said mobile frame, and wherein said hydraulic power means for steering said steerable wheels comprises: a. a hydraulic steering ram extending between said frame and carriage so as to cause rotation of said carriage on said vertical axis; b. fluid conduits connecting said steering ram to said separate pump and source of fluid; and c. control valve means interposed in said fluid conduits of said steering ram for controlling the movement of said wheel carriage in opposite directions on said vertical axis.
 10. The structure of claim 9 in further combination with a pair of opposed trolley carriages, each trolley of said pair of trolley carriages being constructed to have rolling engagement with the upper surface and a different one of opposed side edges of the concrete pavement, a pair of first control rods having opposite ends of each one pivotally connected to a different one of said trolley carriages and said wheel carriage tongue, a pair of second control rods having opposite ends of each one pivotally connected to a different one of said trolley carriages and said wheel carriage, each of said first and second pair of control rods being extensible and retractable, tension means for biasing each of said first pair of control rods in a direction to retract said control rods whereby each one of said trolley carriages is maintained in rolling engagement with a respective side edge of the concrete pavement and means on each of said second control rods for locking said second control rods against said extensible retractable movements.
 11. The structure of claim 9 wherein said steerable wheels include a pair of spaced wheel members mounted for rotation on a horizontal axis extending transversely to the direction of travel of said mobile frame, a pair of hydraulic wheel motors each operatively coupled to a different one of said wheel members, fluid conduits connecting each hydraulic wheel motor to said separate hydraulic pump, and control valve means for controlling the flow of fluids to said hydraulic motors whereby said hydraulic wheel motors may be stopped and started and operated in forward and reverse directions of rotation.
 12. The structure of claim 11 in further combination with a speed control valve connected to said source of fluid and to said control valve means of said hydraulic wheel motors for controlling the speed of operation thereof.
 13. The structure of claim 1 wherein said arm means is a pair of front arms and a pair of rear arms each pivotally connected to respective front and rear portions of said platform and said mobile frame in a parallelogram arrangement and wherein said means for adjusting the depth to which said cutting discs cut into the concrete pavement is a shim interposed between said rear pair of arms and said mobile frame.
 14. The structure of claim 1 wherein said platform includes a shroud enclosing the upper portion of said cutting discs and wherein said means for introducing a flow of liquid coolant to said cutting discs includes a rigid conduit extending along opposite sides of said cutting discs within said shroud, said conduits being formed with apertures for spraying liquid coolant on opposite sides of each of said cutting discs.
 15. A concrete pavement cutting machine comprising: a. a mobile frame including fixed and steerable wheels mounted for movement of said mobile frame along a path of travel; b. a mounting platform underlying said mobile frame; c. arm means mounting said platform to said mobile frame for swinging movements toward and away from the concrete pavement underlying said mobile frame at a constant degree of angular relationship with the plane of the concrete pavement; d. a plurality of cutting discs mounted in tandem on said platform for rotation in a common vertical plane extending longitudinally of the direction of travel of said mobile frame; e. hydraulic power means including engine means for driving said cutting discs, for imparting said movement to said platform, for driving one of said fixed and steerable wheels, and for steering said steerable wheels; and f. means for introducing a flow of liquid coolant to each of said cutting discs; g. said cutting discs being so disposed relative to said mobile frame that each disc rearwardly of the front one of said discs cuts into the pavement at a greater depth from the surface of the pavement than the preceeding disc. 